Composite box structure for a railway car

ABSTRACT

A composite box structure having a core encapsulated in multiple layers of fiber reinforced plastic is provided. The core may be formed from various materials which provide improved resistance to heat transfer between the interior and the exterior of the composite box structure. The composite box structure includes a pair of end walls, a pair of side walls, a floor and a roof with fiber reinforced plastic interior and exterior surfaces. An opening is formed in each side wall to allow access to the interior of the composite box structure. A flexible hinge or joint is integrally molded between each end wall and the respective side walls and between each end wall and the floor. The composite box structure may be mounted on a railway car underframe to provide an insulated composite railway boxcar.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/001,348, filed Jul. 21, 1995; U.S. Provisional Application No.60/001,347, filed Jul. 21, 1995 and U.S. Provisional Application No.60/001/346, filed Jul. 21, 1995.

This application is related to co-pending application entitled InsulatedComposite Railway Boxcar and Method, filed on Jul. 19, 1996, Ser. No.08/684,345, now U.S. Pat. No. 5,765,485, and co-pending applicationentitled Load Divider Assembly and Door Assembly for a Composite RailwayBoxcar, filed on Jul. 19, 1996, Ser. No. 08/684,537, allowed.

TECHNICAL FIELD OF THE INVENTION

This invention relates generally to a composite box structure and moreparticularly to a composite box structure which may be used in themanufacture of various types of railway cars.

BACKGROUND OF THE INVENTION

Over the years, general purpose railway boxcars have progressed fromrelatively simple wooden structures mounted on flat cars to moreelaborate arrangements including insulated walls and refrigerationequipment. Various types of insulated railway boxcars are presentlymanufactured and used. A typical insulated railway boxcar includes anenclosed structure mounted on a railway car underframe. The enclosedstructure generally has an outer shell, one or more layers of insulationand interior paneling. The outer shell of such railway boxcars often hasan exterior surface formed from various types of metal such as steel oraluminum. The interior paneling is often formed from wood and/or metalas desired for the specific application. For some applications theinterior paneling has been formed from fiber reinforced plastic (FRP).Various types of sliding doors including plug type doors are generallyprovided on each side of conventional railway boxcars for loading andunloading freight. Conventional railway boxcars are assembled fromvarious pieces of wood, steel and/or sheets of composite materials suchas fiberglass reinforced plastic. Significant amounts of raw material,labor and time are often required to complete the manufacture andassembly of conventional railway boxcars.

The underframe for many railway boxcars include a center sill with apair of end sills and a pair of side sills arranged in a generallyrectangular configuration corresponding approximately with thedimensions for the floor of the railway boxcar. Cross bearers and crossties are provided to establish the desired rigidity and strength fortransmission of vertical loads from the side sills to the center silland for dissipating horizontal end loads on the center sill to otherportions of the underframe. A plurality of longitudinal stringers arealso provided on each side of the center sill to support the floor ofthe enclosed structure. Examples of such railway car underframes areshown in U.S. Pat. Nos. 2,783,718 and 3,266,441.

For many years various techniques have been used to build fiberglassboat hulls. Many of these hulls have been fabricated using wet layuptechniques in which each layer of material such as fiberglass or carbonfiber is first wetted with the desired resin such as polyester orvinylester and then laid in an open mold. Recently, vacuum baggingtechniques have been combined with wet layup techniques to control theemission of volatile organic compounds. Vacuum bagging also produces astronger structure by eliminating air pockets and excess resin in thefinished product.

More recently, vacuum bagging techniques have been combined with anenhanced resin delivery system which allows the use of a closed moldingsystem and dry layup of core layers and fiber reinforcing layers such asfiberglass in the mold. This process may sometimes be referred to ascomposite resin infusion molding. U.S. Pat. Nos. 4,902,215; 5,052,906and 5,316,462 provide additional information concerning this type ofvacuum bagging process to form a fiberglass reinforced compositearticle.

Various types of load dividers and freight securing systems havepreviously been used to prevent undesired movement of freight containedwithin a railway boxcar. The use of such systems is particularlyimportant when a railway boxcar is only partially loaded. Examples ofsuch systems are shown in U.S. Pat. No. 5,370,482 entitled "CargoSecurement System" and U.S. Pat. No. 5,386,674 entitled "Two PieceBulkhead Door for Rail Cars and the Like." All patents noted in theBackground of the Invention are incorporated by reference for allpurposes within this application.

SUMMARY OF THE INVENTION

In accordance with the present invention, disadvantages and problemsassociated with previous insulated railway boxcars have beensubstantially reduced or eliminated. The present invention provides acomposite box structure for a railway boxcar having enhanced insulation,reduced weight, increased capacity and increased service life ascompared to a typical boxcar. A composite box structure incorporatingteachings of the present invention allows assembly of the resultingrailway boxcar with similar or reduced costs as compared to conventionalrailway boxcars with the same performance characteristics.

One aspect of the present invention includes a composite box structurehaving a pair of side walls, end walls and a floor fabricated as asingle unit using vacuum bagging techniques along with dry layup ofselected material layers and an enhanced resin delivery system. Openingsare provided in the side walls during the molding process to correspondwith the desired location of doors for the resulting railway boxcar. Aroof may be molded as a single unit using the same materials andtechniques as the side walls, end walls and floor.

Technical advantages of the present invention include providing acomposite box structure having completely flush interior and exteriorsurfaces with no seams and no metal fasteners extending throughout theenclosed structure. Internal supporting beams are formed within the sidewalls from the same composite materials used to mold the walls, floorand roof. The floor has a completely flush interior surface with noseams or joints. The resulting composite box structure does not have anymetal heat transfer paths between the exterior and the interior. Also,the resulting composite box structure is waterproof and highly corrosionresistant.

Further technical advantages of the present invention include providinga composite box structure having substantially reduced heat transfercharacteristics resulting from selection of core materials with improvedresistance to heat transfer and no seams or metal fasteners associatedwith assembly of the end walls, side walls and roof. For someapplications, the composite box structure provides sufficient insulationto allow shipping frozen foods without requiring refrigerationequipment. By eliminating metal and other thermal energy transfer pathsbetween the exterior and the interior of the composite box structure,the thickness of insulation materials can be reduced while providingsubstantially increased resistance to heat transfer between the exteriorand the interior.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following writtendescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1A is a schematic drawing in elevation showing a side view of arailway car having a composite box structure incorporating oneembodiment of the present invention;

FIG. 1B is an end view of the railway car of FIG. 1A;

FIG. 2A is a schematic drawing showing an exploded, isometric view of afirst fiber reinforced composite unit and a second fiber reinforcedcomposite unit which may be joined together to form the composite boxstructure of FIGS. 1A and 1B in accordance with one aspect of thepresent invention;

FIGS. 2B, 2C, and 2D are schematic drawings showing exploded, isometricviews of first fiber reinforced composite units and second fiberreinforced composite units which may be joined together to formcomposite box structures in accordance with other aspects of the presentinvention;

FIG. 2E is a schematic drawing showing an isometric view of a boxstructure in the form of a single integrally molded fiber reinforcedcomposite unit.

FIG. 3 is a schematic drawing in section with portions broken awayshowing an interior view of a composite box structure incorporating oneembodiment of the present invention;

FIG. 4 is a schematic drawing in section with portions broken awayshowing a floor with a foam core and multiple plies of fiber material inaccordance with one aspect of the present invention;

FIG. 5 is a schematic drawing in section with portion broken awayshowing the floor of FIG. 4 after the fiber material has been infusedwith a selected resin;

FIG. 6 is an isometric drawing with portions broken away showing aschematic view of a floor and side wall incorporating one embodiment ofthe present invention;

FIG. 7 is a schematic drawing in section and in elevation with portionsbroken away showing integrally molded connections between an end walland a pair of opposite side walls in accordance with one aspect of thepresent invention;

FIG. 8 is a schematic drawing in section and in elevation with portionsbroken away showing a flexible hinge or joint formed between a floor andan end wall in accordance with one aspect of the present invention;

FIG. 9 is a schematic drawing in section and in elevation with portionsbroken away showing a flexible hinge or joint formed between a side walland an end wall in accordance with one aspect of the present invention;

FIG. 10 is a schematic drawing in section and in elevation with portionsbroken away showing an exploded view of a first fiber reinforcedcomposite unit being installed on a second fiber reinforced compositeunit in accordance with one aspect of the present invention;

FIG. 11 is a schematic drawing in section with portions broken awayshowing one embodiment for attaching the roof and end wall of FIG. 10;and

FIG. 12 is a schematic drawing in section and in elevation with portionsbroken away showing a side wall having foam blocks and internal verticalsupport beams in accordance with one embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The preferred embodiments of the present invention and its advantagesare best understood by referring to FIGS. 1A through 12 of the drawings,like numerals being used for like and corresponding parts of the variousdrawings.

Insulated composite railway boxcar 20 incorporating teachings of thepresent invention is shown in FIGS. 1A and 1B with composite boxstructure 30 mounted on railway car underframe 200. As will be explainedlater in more detail, composite box structure 30 is preferably bothadhesively bonded and mechanically engaged with railway car underframe200. For the embodiment of the present invention shown in FIGS. 1A and1B, railway boxcar 20 has exterior dimensions which satisfy therequirements of Plate C and associated structural design requirements ofthe Association of American Railroads (AAR). Forming composite boxstructure 30 from light weight composite materials in accordance withteachings of the present invention allows a reduction in the weight ofrailway boxcar 20 while at the same time increasing both the internalvolume and the load carrying capacity of railway boxcar 20 as comparedto a conventional insulated boxcar within Plate C requirements.

For one application, composite box structure 30 provides hollow interior32 with dimensions of approximately sixty-eight feet in length, ten feetin width and twelve feet in height. For this application, railway boxcar20 has a freight carrying capacity of approximately 6,291 cubic feetwith a light weight of 86,000 pounds and a nominal load carryingcapacity of 200,000 pounds which is very advantageous for an insulatedrailway boxcar satisfying the dimensional requirements of Plate C.Additional specifications for railway boxcar 20 are included at the endof this written description. As a result of the present invention,composite box structure 30 may be modified to accommodate variousgeometric configurations based on specific customer requirementsconcerning the size and type of freight that will be carried in theresulting railway boxcar 20.

For purposes of this patent application, the term "fiber reinforcedplastic" is used to refer to composite materials composed of either athermosetting or thermoplastic resin and fibers, filaments, or whiskersof material such as glass, metal, aramid, boron, carbon, aluminumsilicate and other suitable ceramic materials. For purposes of thispatent application, the term "resin" is used to include both naturallyoccurring and synthetic polymers which may be mixed with variousadditives such as fillers, colorants, plasticizers, and curing agents,to infuse or impregnate the selected fiber material to form the desiredfiber reinforced plastic layers and surfaces during fabrication ofcomposite box structure 30. For one application the fiber materialpreferably includes glass fibers typically associated with FIBERGLAS®products available from Owens-Corning.

Composite box structure 30 is preferably fabricated using vacuum baggingtechniques which include dry lay up of selected core materials andmultiple layers of the selected fiber materials in a closed moldingsystem (not shown) along with an enhanced resin delivery system (notshown). Some of the benefits of using a closed molding system includethe ability to fabricate a large number of composite box structures 30from the same mold with dimensions that meet the selected AAR platerequirements and provide a smooth, aerodynamic exterior surface for theresulting railway boxcar 20.

Closed molding systems and enhanced resin delivery systems may bemodified to form composite box structures 30 with various configurationsand dimensions as required for the specific railway boxcar 20. U.S. Pat.Nos. 4,902,215; 5,052,906 and 5,316,462 show examples of vacuum baggingtechniques satisfactory for use with the present invention. Compositeresin infusion molding processes incorporating various features of thesepatents have been licensed to Hardcore DuPont Composites L.L.C. locatedat 42 Lukens Drive, New Castle, Del. Various types of compositestructures molded in accordance with the teachings of these patents areavailable from Hardcore DuPont.

For the embodiment shown in FIGS. 1A, 1B, 2A, 3 and 10, composite boxstructure 30 is formed from first fiber reinforced composite unit 40 andsecond fiber reinforced composite unit 120. FIGS. 2B, 2C and 2D showalternative configurations of first and second fiber reinforcedcomposite units which may be used to form composite box structure 30.Also, for some applications composite box structure 30 may be integrallymolded as a single fiber reinforced composite unit.

First composite unit 40 includes a pair of opposite side walls 42 and44, a pair of opposite end walls 82 and 84 and floor 100. Side walls 42and 44 along with end walls 82 and 84 and floor 100 cooperate with eachother to partially define hollow interior 32 of composite box structure30. Hollow interior 32 corresponds with the interior of railway boxcar20 in which various types of freight may be placed for shipment inrailway boxcar 20. Second composite unit or roof 120 has dimensionscorresponding with side walls 42 and 44 and end walls 82 and 84 to allowattaching roof 120 with end walls 82 and 84 and side walls 42 and 44opposite from floor 100.

Side walls 42 and 44, end walls 82 and 84 and floor 100 are preferablyintegrally molded with each other using vacuum bagging techniques toform first fiber reinforced composite unit 40. Similar moldingtechniques may be used to form second fiber reinforced composite unit orroof 120. Both first composite unit 40 and second composite unit 120preferably have a foam core covered or wrapped with multiple plies offiber material which has been infused with a selected resin toencapsulate the foam core with one or more layers of fiber reinforcedplastic. The multiple plies of fiber material and the selected resinalso form fiber reinforced plastic interior surfaces and exteriorsurfaces for composite box structure 30. For some applications sidewalls 42 and 44, end walls 82 and 84, floor 100 and roof 120 may beintegrally joined with each other by molding in a closed molding system(not shown) to form a single fiber reinforced composite unit as shown inFIG. 2E. Materials other than foam may be used to form the core.

As shown in FIG. 2A, end walls 82 and 84 extend between and areintegrally molded with respective ends of side walls 42 and 44. Floor100 extends between and is integrally molded with side walls 42 and 44and end walls 82 and 84 to form first fiber reinforced composite unit40. Second fiber reinforced composite unit or roof 120 is molded as aseparate unit and mounted on side walls 42 and 44 and end walls 82 and84 opposite from floor 100 to form composite box structure 30.

As illustrated in FIGS. 3, 6, 9, and 12, first layer 51 of fiberreinforced plastic is preferably disposed on the interior surface ofeach side wall 42 and 44. Second layer 52 of fiber reinforced plastic ispreferably disposed on the exterior surface of each side wall 42 and 44.Each side wall 42 and 44 preferably includes foam core 53 encapsulatedbetween layers 51 and 52 of fiber reinforced plastic.

In a similar manner as shown in FIGS. 7 and 8, first layer 91 of fiberreinforced plastic is preferably disposed on the interior surface ofeach end wall 82 and 84. Second layer 92 of fiber reinforced plastic ispreferably disposed on the exterior surface of each end wall 82 and 84.Each end wall 82 and 84 includes foam core 93 encapsulated betweenlayers 91 and 92 of fiber reinforced plastic. In a similar manner floor100 includes foam cores 103 encapsulated between layers 101 and 102 offiber reinforced plastic. Second composite unit or roof 120 alsoincludes foam core 123 encapsulated between layers 121 and 122 of fiberreinforced plastic. As will be explained later in more detail theconfiguration of foam cores 53, 103 and 123 may be varied in accordancewith the teachings of the present invention depending upon therequirements of the resulting railway boxcar 20.

As a result of the molding process first layers 51, 91 and 101 provide acontinuous, smooth interior surface of fiber reinforced plastic forrailway boxcar 20. In a similar manner exterior surfaces 52, 92 and 102are integrally molded with each other to form a continuous, smoothexterior surface of fiber reinforced plastic for railway boxcar 20.

Foam cores 53, 93, 103 and 123 may be formed from various types ofmaterial such as urethane, polyurethane, styrene and polystyrene. Forsome applications cores 53, 93, 103 or 123 may be formed with lightmetal foam. Also, foam cores 53, 93, 103 and 123 may have variousconfigurations such as foam blocks wrapped with one or more plies of aselected fiber material or layers of a selected foam materialalternating with plies of a selected fiber material. For still otherapplications foam cores 53 and/or 103 may be replaced with light weightwood such as balsa wood or a heavier wood such as plywood.

The selected foam core and multiple plies of fiber material are placedin a closed molding system having the desired configuration for firstcomposite unit 40 or second composite unit 120. A resin delivery systemis used to infuse or impregnate the multiple plies of fiber materialwith the selected resin. Depending upon the intended application for theresulting railway boxcar 20, the fiber material may include carbon,boron, graphite, glass, aramid or a combination of these materials.Aramids such as KEVLAR® fibers and NOMEX® fibers available from E. I.DuPont De Nemours & Co. may be particularly useful in fabricatingrailway box cars. Other fiber materials may be satisfactorily used withthe present invention. Again, depending upon the intended applicationfor railway boxcar 20, the resin may be selected from a wide variety ofpolymers including epoxy, polyester, vinylester and vinyl. Also, otherresins may be satisfactorily used with the present invention.

By properly selecting the type of material used to form foam cores 53,93, 103 and 123 along with other teachings of the present inventionwhich substantially reduce or minimize potential heat transfer paths,composite box structure 30 may have a heat transfer rate ofapproximately one hundred sixteen (116) BTUs per hour per degreeFahrenheit or less. As shown in FIGS. 6, 9, and 12 foam core 53 for sidewalls 42 and 44 may be formed from a plurality of foam blocks 53 whichhave been wrapped with the selected fiber material and impregnated withthe selected resin during the molding process. Foam core 103 for floor100 may also be formed from a plurality of foam blocks wrapped withfiber material and impregnated with the selected resin during themolding process.

For some applications foam core 93 for end walls 82 and 84 may alsoinclude a plurality of foam blocks similar to foam blocks 53 or 103which have been wrapped with fiber material and impregnated with theselected resin during the molding process. Foam core 123 for roof 120may also be formed from a plurality of foam blocks.

Alternatively, foam cores 53, 93, 103 and/or 123 may be formed from agrid of the selected foam material alternating with plies of theselected fiber material. The configuration of the layers of foammaterial and fiber material may be varied to provide the desiredstructural strength for the respective side walls 42 and 44, end walls82 and 84, floor 100 and roof 120. FIGS. 7 and 8 show grid 86 ofalternating foam material and plies of fiber material sandwiched betweenmultiple layers of fiber material and infused with the selected resin toform end walls 82 and 84. The vertical and horizontal plies of fibermaterial may be continuous or discontinous as desired for the selectedend wall.

Corresponding interior surfaces 91 have at least one layer of fiberreinforced plastic and corresponding exterior surfaces 92 also has atleast one layer of fiber reinforced plastic. For one application twoplies of fiber material were used to form interior surface 91 andexterior surface 92. The fiber materials within the grid are infusedwith resin to form a web of fiber reinforced plastic layersencapsulating the foam material. For one application end walls 82 and 84have been formed with this grid configuration having continuoushorizontal plies of fiber material and discontinuous vertical plies offiber material. Side walls 42 and 44, floor 100 and roof 120 may also beformed with a similar grid configuration if desired.

For some applications, the resulting composite box structure 30 may bepainted or covered with coating materials that reflect solar energy fromthe sun. For example, a coating material containing ceramic fibers (notexpressly shown) can be applied to the exterior surfaces of compositebox structure 30 to significantly reduce the amount of heat absorbedfrom ultraviolet rays and infrared rays. By using such coatingmaterials, the thickness of foam cores 53, 93, 103 and/or 123 may bereduced while maintaining the same level of insulation or theeffectiveness of the insulation may be increased for the same thicknessof foam cores. For some applications the coating material may be appliedas part of the resin infusion process. For other applications thecoating material may be applied after fabrication of composite boxstructure 30 has been completed. Coating systems with various ceramicfibers are available from Energy Research Center in Houston, Tex. Also,3M Company has available various types of thin film or sheet materialthat may be applied to the exterior of composite box structure 30 toreflect solar energy.

During the molding process a generally rectangular opening 46 is formedin each side wall 42 and 44 intermediate the ends of the respective sidewalls 42 and 44. Door 180 is slidably mounted on each side wall 42 and44 adjacent to the respective opening 46 for use in controlling accessto interior 32 of railway boxcar 20. The height of each opening 46preferably extends from floor 100 to the adjacent edge of secondcomposite unit or roof 120. The center of each opening 46 correspondsapproximately with the midpoint in the respective side wall 42 and 44.For one application each opening 46 has a height of approximately ninefeet six inches which corresponds to the height of the respective sidewalls 42 and 44 between adjacent portions of floor 100 and roof 120.

Each door 180 has a first position blocking the respective opening 46 toform a thermal barrier between hollow interior 32 and the exterior ofrailway boxcar 20. Each door 180 also has a second position which allowsaccess to hollow interior 32 of railway boxcar 20 through the respectiveopenings 46. A pair of door stops 181 and 182 are preferably mounted onthe exterior of each side wall 42 and 44 to limit the longitudinalmovement of the respective door 180 from its first position to itssecond position. In FIG. 1A, door 180 is shown slidably mounted on uppertrack 194 and lower track 196 intermediate its first position whichblocks opening 46 and its second position in which edge 183 of door 180contacts its respective door stops 181 and 182. For some application,doors 180 may be formed from the same composite materials as compositebox structure 30.

As shown in FIGS. 1A and 1B, railway car underframe 200 includes a pairof railway trucks 202 and 204 located adjacent to each end of railwayboxcar 20. Safety equipment such as ladders 206 and hand brake 208 areattached to railway car underframe 200 with no connections orattachments to composite box structure 30. Standard railway couplings210 are also provided at each end of railway car underframe 200. Eachcoupling 210 preferably includes end of car cushioning unit 212 disposedbetween each end of center sill 214 and the respective coupling 210. Oneof the technical benefits of the present invention includes the abilityto add end of car cushioning units 212 having different lengths oftravel, depending upon the intended application for the resultingrailway boxcar 20. For some applications, cushioning units 212 may havea length of travel of approximately fifteen (15) inches. For otherapplications, cushioning units 212 may have a length of travel ofapproximately eighteen (18) inches or more.

FIGS. 2B, 2C and 2D show alternative configurations of a first fiberreinforced composite unit and a second fiber reinforced composite unitwhich may be attached to each other to form composite box structure 30.In FIG. 2B, side walls 42 and 44, end walls 82 and 84 and roof 120 havebeen integrally molded with each other to form first fiber reinforcedcomposite unit 301. Second fiber reinforced composite 302 is provided toform floor 100 for the resulting composite box structure 30.

In FIG. 2C, first fiber reinforced composite unit 303 and secondcomposite unit 304 have been formed with substantially identicaldimensions and configurations. First composite unit 303 and secondcomposite unit 304 are essentially mirror images of each other whichcorrespond to one-half of composite box structure 30. Therefore, thesame closed mold may be used to form first fiber reinforced compositeunit 303 and second fiber reinforced composite unit 304. Composite boxstructure 30 may be formed by attaching first composite unit 303 withsecond composite unit 304.

FIG. 2D shows first fiber reinforced composite unit 305 and second fiberreinforced composite unit 306 which also have substantially identicaldimensions and configurations corresponding to cutting composite boxstructure 30 along its longitudinal centerline. Thus, first fiberreinforced composite unit 305 and second fiber reinforced composite 306may be formed in the same closed mold. First fiber reinforced compositeunit 305 and second fiber reinforced composite unit 306 may be attachedto each other to form composite box structure 30 as shown in FIG. 2D.

For one application composite box structure 30 is formed by mountingroof 120 on end walls 82 and 84 and side walls 42 and 44 opposite fromfloor 100 to define hollow interior 32. For purpose of illustration,line 72 is shown in FIGS. 1 and 3 to represent the seam or joint betweenroof 120 and first fiber reinforced composite unit 40. Normally, seam orjoint 72 between roof 120 and first composite unit 40 will be sealed andcovered using conventional fiberglass fabrication techniques such thatseam 72 is not visible on either the interior or the exterior ofcomposite box structure 30. Adhesive bonding around the full perimeterof seam 72 will provide a strong, water tight seal between roof 120 andfirst fiber reinforced composite unit 40.

Roof 120 has a generally rectangular configuration with a lengthcorresponding approximately to the length of side walls 42 and 44 andthe length of floor 100. The width of roof 120 corresponds approximatelyto the width of end walls 82 and 84 and the width of floor 100. As shownin FIG. 3, interior surface 121 of roof 120 has a generally concaveconfiguration and exterior surface 123 has a generally correspondingconvex configuration. For one application, roof 120 may have an overallinside radius of approximately thirteen feet four inches with aninterior radius of approximately three inches and an exterior radius ofeight inches around the perimeter of roof 120.

As shown in FIGS. 3 and 10, foam core 123 of roof 120 is divided byfiber reinforced plastic layers 126 and 128 into three longitudinalsections 123a, 123b and 123c. Fiber reinforced plastic layers 126 and128 are preferably disposed on opposite sides of the longitudinalcenterline of roof 120 and extend over the full length of roof 120.Fiber reinforced plastic layers 126 and 128 provide structural strengthfor roof 120 while at the same time allowing for limited flexing and/ortwisting of roof 120 during movement of the associated railway car 20.Fiber reinforced plastic layers 126 and 128 function as longitudinalstiffeners for roof 120.

For some applications, flanges 124 are formed along longitudinal edges125 and extend from interior surface 121. Each flange 124 is sized toengage a portion of the interior surfaces of the respective side walls42 and 44 when roof 120 is attached to end walls 82 and 84 and sidewalls 42 and 44. Metal supporting plates (not expressly shown) may beintegrally molded in side walls 42 and 44 for attachment with respectiveflanges 124.

As shown in FIG. 3, upper load divider track assembly 140 includes apair of tracks 142 and 144 with portions of each track mounted on anddisposed between the respective side walls 42 and 44 and roof 120. Aplurality of bracket assemblies 146 are used to secure tracks 142 and144 on interior surface 51 of the respective side walls 42 and 44adjacent to interior surface 121 of roof 120.

Portions of lower load divider track assembly 170 are also shown in FIG.3 having a pair of tracks 172 and 174 disposed respectively within firstlongitudinal recess 61 and second longitudinal recess 62. Firstlongitudinal recess 61 is formed in interior surface 51 of side wall 42located above interior surface 101 of floor 100. Second longitudinalrecess 62 is formed within interior surface 51 of side wall 42 locatedabove interior surface 101 of floor 100. Tracks 172 and 174 extendgenerally parallel with each other, tracks 142 and 144 and floor 100.

For some applications, all or a portion of layers 51, 52, 91, 92, 121and 122 may be formed from two or more plies of fiber material (notexpressly shown). For example, three or four plies of fiber material maybe used to form reinforced strike zones 54 and 55 as part of interiorsurface 51 adjacent to and extending longitudinally parallel with floor100. Strike zones 54 and 55 provide increased resistance to damagecaused by freight contacting inside surface 51 of the respectivesidewalls 42 and 44. The thickness of strike zones 54 and 55 as shown inFIG. 3 is exaggerated for the purpose of illustration. One of thetechnical benefits of the present invention includes providing multipleplies of fiber material to reinforced selected portions of either theinterior surface or the exterior surface of composite box structure 30.

For some applications railway car underframe 200 preferably includes aplurality of longitudinal stringers 230. Each longitudinal stringer 230has a first surface 231 and a second surface 232. Portions of exteriorsurface 102 of floor 100 of composite box structure 30 may be adhesivelybonded with first surfaces 231 of longitudinal stringers 230. FIGS. 4and 5 are schematic representations showing portions of floor 100disposed on longitudinal stringers 230.

For purposes of illustrating various aspects of the present invention, aportion of floor 100 is shown in FIG. 4 as they would appear withouthaving first been infused with a selected resin. Normally, composite boxstructure 30 is only mounted on railway car underframe 200 aftercompletion of the molding process which includes infusion with theselected resin.

As illustrated in FIG. 4, floor 100 preferably includes a plurality offoam blocks 103 which have each been wrapped with one or more plies offiber material 104. During the molding process, foam blocks 103 aredisposed adjacent to each other and extend over the length and width offloor 100. This configuration results in vertical plies 105 of fibermaterial disposed between adjacent foam blocks 103 extendinglongitudinally along the length of floor 100. First ply 106 of fibermaterial is disposed on the interior portions of foam blocks 103. Asecond ply 108 of fiber material is disposed on the exterior of foamblocks 103.

For some applications, floor 100 could then be formed by infusing ormolding first ply 106, fiber layers 104 and second ply 108 with theselected resin. The use of vacuum bagging techniques and dry layup ofthe selected core materials and multiple layers of the selected fibermaterial allow varying the cross section associated with floor 100depending upon the specific application in which the resulting railwayboxcar 20 will be used.

For many applications, foam blocks 103 will not carry compression andshear forces associated with placing a heavy load such as a forkliftmoving cargo on interior surface 101 of floor 100. Thus, layer 110 of afelt type material such as polyester is preferably placed on first fiberply 106 along with two additional plies 112 and 114 of fiber material.The configuration of felt type material 110 and multiple plies of fibermaterial 104, 106, 112 and 114 results in providing a thick layer 116 offiber-reinforced plastic extending over the length and width of interiorsurface 101 of floor 100.

The width of foam blocks 103 is preferably selected to be approximatelyequal to the distance between the centerline of adjacent longitudinalstringers 230. Thus, vertical layers 105 of fiber material are locatedwithin floor 100 at a position corresponding approximately with theposition of respective longitudinal stringer 230 in railway carunderframe 200. Infusion of fiber material plies 104, 106 108, 112 and114 along with felt layer 110 results in forming a continuous web offiber reinforced plastic which encapsulates foam blocks 103. Thus, anyloads placed on interior surface 101 of floor 100 are transmittedthrough thick layer 116 of fiber reinforced plastic to vertical layers118 of fiber reinforced plastic and onto the respective longitudinalstringer 230 to provide the desired load carrying capacity for floor100.

Plies of fiber material 104, 106, 108, 112 and 114 may be formed fromthe same types of material. Alternatively, plies 104, 106, 108, 112 and114 may be formed from different types of fiber material to provide thedesired strength for floor 100. When the fiber plies are infused withthe selected resin, the resulting structure is a thick, continuous webof fiber reinforced plastic 116 and 118 as shown in FIG. 5. As shown inFIGS. 2A and 3, fiber reinforced plastic interior surface 101 of floor100 provides a generally smooth, continuous, flush surface with noindentations or openings which allows for easier cleaning. For oneapplication floor 100 has a thickness of approximately six inches.

FIG. 6 shows a portion of side wall 44 and floor 100 adjacent to therespective opening 46. This portion of wall 42 has been formed bywrapping a plurality of foam blocks 53 with the selected fiber material.During the molding process, foam blocks 53 are placed in a closed moldbetween a first ply of fiber material and a second ply of fibermaterial. For some applications, multiple plies of fiber materials maybe used to wrap foam blocks 53 and multiple layers of fiber material maybe disposed on what will eventually become the interior surface 51 andthe exterior surface 52 of wall 42. The fiber material plies are thenimpregnated with the selected resin to form a continuous web offiber-reinforced plastic layers between adjacent foam blocks andfiber-reinforced plastic layers 51 and 52. As shown in FIGS. 5, 6, 9,and 12, the closed molding system and infusion of resin results in acontinuous web of fiber-reinforced plastic. For some application foamblocks 53 may be coated or treated to prevent foam blocks 53 fromabsorbing or being infused with the selected resin. Side wall 44 has asimilar cross section.

For some applications end walls 82 and 84 along with roof 120 and floor100 may also be formed from a plurality of foam blocks encapsulated inlayers of fiber reinforced plastic. One of the technical advantages ofthe present invention includes the ability to select various types offoam and fiber materials and to vary the configuration of thesematerials to enhance the performance of the resulting composite boxstructure 30.

For example, the thickness of foam core 53 is substantially reduced insection 48 of side wall 44 immediately adjacent to opening 46. Three orfour plies of fiber material may be used to form section 48 of side wall44 to provide more strength and resistance to wear at opening 46. Thereduced thickness of section 48 allows installation of door 180 and theassociated vertical portion of door frame 190. A portion of one of thevertical support beams 56 which are preferably formed in each side wall44 and 42 is shown in FIG. 6.

During movement of railway car 20, freight placed within hollow interior32 may tend to shift. Considerable force may be applied to end walls 82and 84 by such shifting while starting and stopping movement of theassociated railway boxcar 20. FIGS. 7, 8, 9, 10 and 11 show variousfeatures of the present invention which result in strengthening theconnection between side walls 42 and 44, end walls 82 and 84, floor 100and roof 120. For purposes of illustration fiber reinforced plasticlayer associated with interior surface 91 is shown broken away in FIG.7.

To increase the strength of the integrally molded connections betweenend wall 82 and adjacent portions of side walls 42 and 44, a pluralityof end supporting layers (not expressly shown) of fiber reinforcedplastic may be formed to extend from vertical support beam 56 in sidewall 44 through end wall 82 to a corresponding vertical support beam 56in side wall 42. During the molding process, one or more plies of fibermaterial may be placed within side walls 42 and 44 and extending throughend wall 82 to provide the desired end supporting layers. As part of themolding process respective ends of the plies of fiber materials whichwill eventually become the end supporting layers are preferable placedin close contact with the plies of fiber material which will eventuallybecome vertical support beam 56. As previously noted during the resininfusion process, a continuous web of fiber reinforced plastic is formedin each of the plies of fiber material associated with side walls 42 and44 and end walls 82. Thus, any forces applied to the end supportinglayers and end wall 82 will be transmitted to the respective verticalsupport beams 56 and side walls 42 and 44 in shear.

End supporting layers may be incorporated as part of end wall 82 havingeither foam blocks or a grid of alternating layers of foam and fibermaterial as shown in FIG. 7. U.S. Pat. No. 5,052,906 shows examples ofusing multiple layers of fiber material and a grid type resindistribution system which may be satisfactorily used to form end wall82.

During the molding process, corner 58 is formed between the adjacentedges of side wall 42 and end wall 82. Corner 60 is formed between theend of side wall 44 and end wall 82. For one application, the exteriorsurface at corners 58 and 60 has a radius of approximately three inches.The interior surfaces at corners 58 and 60 intersect at approximately aninety degree (90° ) angle. The longitudinal distance between verticalsupporting beams 56 and the respective corners 58 and 60 may beapproximately twenty-four inches.

As previously noted, considerable force may be applied to end walls 82and 84 during movement of the associated railway boxcar 20. Tocompensate for this force, flexible joint 88 as shown in FIG. 8 ispreferably integrally molded between and extending from each end offloor 100 and the respective end walls 82 and 84. For the example showin FIG. 8, end wall 82 is longitudinally spaced from the end of floor100 with a relatively thick layer 90 of fiber reinforced plasticextending between floor 100 and end wall 82. For some applications layer90 may have a thickness which is more than twice the normal thickness offiber reinforced plastic layers 91 and 92 of end wall 82. For oneapplication seven plies of fiber material have been used to form layer90 and five plies of fiber material to form a portion of exterior layer92 adjacent thereto. A block of filler material 96 may be disposed inthe offset formed between the end of floor 100 and end wall 82 toprovide a smooth, aerodynamic configuration. Block 96 is preferably notencapsulated with fiber reinforced plastic during the molding process.

FIG. 9 shows flexible joint 68 which has been integrally molded betweenand extending from end wall 82 and side wall 44 at corner 60. A similarflexible joint 68 is preferably integrally molded and extending betweeneach end of side walls 42 and 44 and the respective end walls 82 and 84.For the example shown in FIG. 9, end wall 82 is longitudinally spacedfrom the end of side wall 44 with a relatively thick layer 70 of fiberreinforced plastic extending between side wall 44 and end wall 82. Forsome applications layer 70 has a thickness which is more than twice thenormal thickness of fiber reinforced plastic layers 91 and 92 of endwall 82. For example layer 70 may be formed from four layers of fibermaterial while layers 91 and 92 are generally formed from only twolayers of fiber material.

Block 76 of filler material may be disposed within the interior ofcomposite box structure 30 in the offset formed between the end of sidewall 44 and end wall 82. The dimensions of filler block 76 are selectedto provide a smooth interior surface for composite box structureadjacent to corner 60. Filler blocks 76 are preferably not encapsulatedwith fiber reinforced plastic during the molding process.

For some applications a reinforcing beam (not expressly shown) may belocated within the interior of composite box structure 30 at respectiveend walls 82 and 84 adjacent to roof 120. Each reinforcing beam may becoupled with the respective end wall 82 and 84 and the respective sidewalls 42 and 44. Each reinforcing beam may include a core encapsulatedin one or more layers of fiber reinforced plastic. For one applicationthe reinforcing beam is formed using a balsa core. During the moldingprocess, tabs of fiber reinforced plastic may be formed to extend fromthe reinforcing beam. The tabs are sized to fit between the upper edgeof end walls 82 and side walls 42 and 44 and the corresponding edges ofroof 120. The reinforcing beam is preferably sized to fit between firstfiber reinforced composite unit 40 and second fiber reinforced compositeunit 120.

For the embodiment as shown in FIGS. 10 and 11 end 130 of roof 120 andthe adjacent portion 132 of end wall 82 may have a substantiallyincreased thickness 136. The exterior surface of end 130 and theadjacent portion 132 preferably have matching curved surfaces selectedto optimize the aerodynamic performance of the resulting composite boxstructure 30.

In FIG. 11 the joint or seam between roof 120 and end wall 82 is shownas relatively smooth matching surfaces 137. For some applicationsmatching grooves or recesses (not expressly shown) may be formed insurfaces 137 to enhance the bonding or seal formed between roof 120 andend wall 82. Alternatively, surfaces 137 may extend at an angle otherthan horizontal as shown in FIG. 11. For some applications surfaces 137may extend at an angle of 45° relative to interior surface 91 of endwall 82. These same techniques may be used to improve the seal betweenroof 120 and adjacent portions of side walls 42 and 44.

For some applications, the strength of side walls 42 and 44 may besubstantially increased by forming a plurality of vertical supportingbeams 56 during the molding process. As shown in FIGS. 6, 7, and 12 afirst group of relatively large foam blocks 53 may be wrapped with fibermaterial. A second group of smaller foam blocks 156 may be wrapped withfiber material and disposed vertically between adjacent foam blocks 53.As shown in FIGS. 6, 7 and 12, the alternating configuration of firstfoam blocks 53 and second foam blocks 156 provides substantial strengthfor side walls 42 and 44. Infusing the fiber material on the exterior ofthe first group of foam blocks and the fiber material on the exterior ofthe second group of foam blocks forms a continuous web of fiberreinforced plastic layers with vertical layers 158 of fiber reinforcedplastic extending between interior surface 51 and exterior surface 52.

For some applications interior surface or first layer 51 of fiberreinforced plastic is preferably formed from at least two plies of theselected fiber material adjacent to each vertical support beam 56.Exterior surface or second layer 52 of fiber reinforced plastic ispreferably formed from at least three plies of the selected fibermaterial adjacent to each vertical support beam 56.

The following specifications are for railway boxcar 20 incorporating oneembodiment of the present invention.

    ______________________________________    Outside length         68 feet 0 inches    Inside length          67 feet 2 inches    Distance between centerline of railway trucks                           50 feet 0 inches    Outside width of composite box structure                           10 feet 0 inches    Inside width            9 feet 2 inches    Height from rail to top of car                           15 feet 6 inches    Inside height from floor to roof                           11 feet 1/2 inch    Height of door opening  9 feet 61/2 inches    Width of door opening  12 feet 0 inches    Internal volume with load dividers                            6,170 cubic feet    Internal volume without load dividers                            6,291 cubic feet    Light weight            86,000 pounds    Nominal load carrying capacity                           200,000 pounds    Total gross rail load  286,000 pounds    ______________________________________

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the following claims.

What is claimed is:
 1. A composite box structure for mounting on arailway car underframe to form an insulated railway boxcar comprising:apair of opposite side walls and a pair of opposite end walls extendingbetween and joined with the side walls to define in part a hollowinterior for the box structure; a floor extending between and joinedwith the side walls and the end walls; an opening formed in each sidewall intermediate the end walls; the side walls, the end walls, and thefloor being a first fiber reinforced composite unit; and a roof formedas a second fiber reinforced composite unit, the roof being mounted onthe end walls and the side walls opposite from the floor.
 2. Thecomposite box structure of claim 1 wherein the first fiber reinforcedcomposite unit includes:a plurality of blocks, each block being wrappedwith a fiber material; the blocks being disposed between a first layerof fiber material and a second layer of fiber material; and the fibermaterial wrapped on the blocks and the first layer of fiber material andthe second layer of fiber material being impregnated with a resin toform a continuous web of fiber reinforced plastic interposed betweeneach pair of adjacent blocks and fiber reinforced plastic layers on theinterior and the exterior of the first fiber reinforced composite unit.3. The composite box structure of claim 1 wherein the second fiberreinforced composite unit includes:a plurality of foam blocks each foamblock being wrapped with a fiber material; the foam blocks beingdisposed between a first layer of fiber material and a second layer offiber material; and the fiber material wrapped on the foam blocks andthe first layer of fiber material and the second layer of fiber materialbeing impregnated with a resin to form fiber reinforced plastic websbetween each adjacent pair of foam blocks and an interior surface and anexterior surface of fiber reinforced plastic layer on the second fiberreinforced composite unit.
 4. The composite box structure of claim 1further comprising:a plurality of foam blocks selected from the groupconsisting of urethane, polyurethane, styrene, polystyrene, and lightmetal foam; material fibers selected from the group consisting ofcarbon, boron, graphite, glass and aramid; and a resin selected from thegroup consisting of epoxy, polyester, vinylester and vinyl.
 5. Thecomposite box structure of claim 1 wherein the first fiber reinforcedcomposite unit further includes a plurality of blocks, each block beingencapsulated in fiber reinforced plastic.
 6. The composite box structureof claim 1 wherein:the floor is formed in part from a plurality ofblocks covered with multiple plies of fiber material; each end wall hasa core disposed between plies of fiber material; the fiber material ofthe floor and the end walls is impregnated with a resin to formcontinuous layers of fiber reinforced plastic; and each end wall isspaced longitudinally from the respective end of the floor with a layerof fiber reinforced plastic extending therebetween to allow limitedmovement of the respective end wall relative to the floor.
 7. Thecomposite box structure of claim 6 wherein the respective fiberreinforced plastic layer joining each end wall with the floor has athickness substantially greater than the thickness of the fiberreinforced plastic layers associated with the respective end wall. 8.The composite box structure of claim 1 wherein:each side wall is formedin part from a plurality of blocks covered with plies of fiber material;each end wall has a foam core with fiber material disposed therein; thefiber material of the side wall and the end walls is impregnated with aresin to form continuous layers of the reinforced plastic; and each endwall is spaced longitudinally from the respective end of the side wallswith a layer of fiber reinforced plastic interposed therebetween toallow limited movement of the respective end wall relative to the sidewalls.
 9. The composite box structure of claim 8 wherein the fiberreinforced plastic layers joining each end wall with the side walls hasa thickness substantially greater than the thickness of the fiberreinforced plastic layers associated with the respective end wall. 10.The composite box structure of claim 1 wherein each side wall includes:aplurality of first foam blocks wrapped with fiber material; the firstfoam blocks being spaced apart longitudinally with respect to each otherto form portions of the respective side wall; a plurality of second foamblocks wrapped with fiber material and disposed vertically betweenadjacent pairs of first foam blocks to provide internal vertical supportbeams for the respective side wall; a first layer of fiber materialdisposed on the exterior of the foam blocks and a second layer of fibermaterial disposed on the interior of the foam blocks; the fiber materialbeing impregnated with a resin.
 11. The composite box structure of claim1 wherein the floor includes:a plurality of foam blocks wrapped withfiber material and disposed adjacent to each other over the length andwidth of the floor; a first layer of fiber material disposed on theinterior of the foam blocks and a second layer of fiber materialdisposed on the exterior of the foam blocks; a layer of felt materialdisposed on the first layer of fiber material with two or moreadditional layers of fiber material disposed on the felt materialopposite from the second layer of fiber material; the fiber materialbeing impregnated with a resin to form a continuous web of fiberreinforced plastic layers encapsulating the foam blocks and forming afiber reinforced plastic interior surface and a fiber reinforced plasticexterior surface for the floor.
 12. A composite box structure formounting on a railway car underframe to form an insulated railway boxcarcomprising:a pair of opposite side walls and a pair of opposite endwalls extending between and joined with the side walls at respectiveends of each side wall; a floor extending between and joined with theside walls and the end walls; the side walls, the end walls and thefloor cooperating with each other to define in part a hollow interiorfor the composite box structure; the side walls, the end walls and thefloor each having an exterior surface which defines in part acorresponding exterior surface of the composite box structure; the sidewalls, the end walls and the floor each having an interior surface whichdefines in part a corresponding interior surface of the composite boxstructure; an opening formed in each side wall intermediate the endwalls with each opening and having a height corresponding approximatelywith the height of each side wall; the side walls, the end walls and thefloor being integrally molded with each other to form a first fiberreinforced composite unit; and a roof formed as a second fiberreinforced composite unit with dimensions corresponding to the end wallsand the side walls to allow attaching the roof to the end walls and theside walls opposite from the floor.
 13. The composite box structure ofclaim 12 wherein:the interior surface of each side wall, end wall andfloor is a layer of fiber reinforced plastic; the exterior surface ofeach side wall, end wall and floor is a layer of fiber reinforcedplastic; and each side wall, end wall and floor has a foam core betweenthe layers of fiber reinforced plastic.
 14. The composite box structureof claim 12 wherein each end wall includes:a grid of foam materialalternating with layers of fiber reinforced plastic; the interiorsurface having a layer of fiber reinforced plastic and the exteriorsurface having a layer of fiber reinforced plastic with the grid of foammaterial and fiber reinforced plastic layers encapsulated therebetween.15. The composite box structure of claim 12 wherein the roof includes:anexterior surface which defines in part a corresponding exterior surfaceof the composite box structure; an interior surface which defines inpart a corresponding interior surface of the composite box structure;the interior surface of the roof being formed from fiber reinforcedplastic; the exterior surface of the roof being formed from fiberreinforced plastic;and the roof having a foam core encapsulated withfiber reinforced plastic.
 16. The composite box structure of claim 12wherein:the roof has a generally rectangular configuration with a lengthcorresponding approximately to the length of the side walls and a widthcorresponding approximately to the width of the end walls; the roof hasan interior surface formed from fiber reinforced plastic; a plurality offlanges extend from the interior surface of the roof; and each flange issized to engage a portion of the interior surface of the respective sidewalls when the roof has been attached to the end walls and the sidewalls.
 17. A composite box structure for mounting on a railway carunderframe to form an insulated railway boxcar comprising:a pair ofopposite side walls and a pair of opposite end walls extending betweenand joined with the side walls at respective ends of each side wall; afloor extending between and joined with the side walls and the endwalls; the side walls, the end walls, and the floor cooperating witheach other to define in part a hollow interior for the box structure; anopening formed in each side wall intermediate the end walls to allowaccess to the hollow interior; the side walls, the end walls and thefloor being integrally molded with each other to form a first fiberreinforced composite unit; and a roof formed as a second fiberreinforced composite unit; the roof being mounted on the end walls andthe side walls opposite from the floor; the side walls, end walls andfloor each having an interior surface formed from fiber reinforcedplastic; the side walls, end walls and floor each having an exteriorsurface formed from fiber reinforced plastic; and the side walls, endwalls and floor each having a foam core encapsulated with fiberreinforced plastic.
 18. The composite box structure of claim 17 whereinthe roof includes:a foam core divided into three sections by two fiberreinforced plastic layers; the two fiber reinforced plastic layersextending longitudinally parallel with a longitudinal centerline of theroof.
 19. 20. The composite box structure of claim 17 wherein:each endwall is spaced longitudinally from the respective end of the floor; aflexible joint is integrally molded between and extends from each end ofthe floor and the respective end wall; the flexible joint having atleast one layer of fiber reinforced plastic integrally molded betweenthe respective end of the floor and the respective end wall.
 21. Thecomposite box structure of claim 17 wherein:each side wall is spacedlongitudinally from the respective end of the floor; a flexible joint isintegrally molded between and extends between each end of the floor andthe respective side wall; and the flexible joint having at least onelayer of fiber reinforced plastic integrally molded between therespective end of the floor and the respective side wall.
 22. Thecomposite box structure of claim 17 wherein:a flexible joint isintegrally molded with and extends between each end of the floor and therespective end wall; a flexible joint is integrally molded with andextends between each end of each side wall and the respective end wall;and a block of filler material is disposed on the exterior of thecomposite box structure adjacent to each flexible joint between thefloor and the end walls to provide a uniform flush exterior for thecomposite box structure at the respective flexible joint.
 23. Thecomposite box structure of claim 17 wherein the floor includes:aplurality of foam blocks wrapped with fiber material and disposedadjacent to each other over the length and width of the floor; a layerof fiber material disposed vertically between adjacent foam blocks andeach vertical layer extending longitudinally along the length of thefloor; a first layer of fiber material disposed on the interior of thefoam blocks and a second layer of fiber material disposed on theexterior of the foam blocks; a layer of felt material disposed on thefirst layer of fiber material with at least two additional layers offiber material disposed on the felt material opposite from the firstlayer of fiber material; the fiber material being impregnated with aresin to form vertical layers of fiber reinforced plastic betweenadjacent blocks and between the fiber reinforced plastic interiorsurface and exterior surface of the floor, each vertical layer of fiberreinforced plastic in the floor being located such that it is adapted tobe positioned substantially vertically above a correspondinglongitudinal stringer of a railway car underframe so that loads placedon the floor are transmitted through the vertical layers of fiberreinforced plastic to the longitudinal stringers.
 24. A composite boxstructure for mounting on a railway car underframe to form an insulatedrailway boxcar comprising:a pair of opposite side walls and a pair ofopposite end walls extending between and joined with the side walls atrespective ends of each side wall; a floor extending between and joinedwith the side walls and the end walls; a roof extending between andjoined with the side walls and the end walls opposite from the floor;the side walls, the end walls, the floor and the roof cooperating witheach other to define in part a hollow interior for the box structure; agenerally rectangular opening formed in each side wall intermediate theend walls to allow access to the hollow interior; the side walls, theend walls, the floor and the roof each having an interior surface whichdefines in part a corresponding interior surface of the composite boxstructure; the side walls, the end walls, the floor and the roof eachhaving an exterior surface which defines in part a correspondingexterior surface of the composite box structure; the side walls, the endwalls, the floor and the roof being integrally molded with each other toform a fiber reinforced composite unit having a foam core encapsulatedwith fiber reinforced plastic; the interior surfaces of the side walls,the end walls, the floor and the roof being formed from fiber reinforcedplastic; and the exterior surfaces of the side walls, the end walls, thefloor, and the roof being formed from fiber reinforced plastic.
 25. Acomposite box structure for mounting on a railway car underframe to forman insulated railway boxcar comprising:a pair of opposite side walls anda pair of opposite end walls extending between and joined with the sidewalls at respective ends of each side wall; a floor extending betweenand joined with the side walls and the end walls; the side walls, theend walls, and the floor cooperating with each other to define in part ahollow interior for the box structure; a generally rectangular openingformed in each side wall intermediate the end walls to allow access tothe hollow interior; the side walls, the end walls and the floor eachhaving an interior surface which defines in part a correspondinginterior surface of the composite box structure; the side walls, the endwalls and the floor each having an exterior surface which defines inpart a corresponding exterior surface of the composite box structure;the side walls, the end walls and the floor being integrally molded witheach other to form a first fiber reinforced composite unit having a foamcore encapsulated with fiber reinforced plastic; the interior surfacesof the side walls, the end walls and the floor being formed from fiberreinforced plastic; the exterior surfaces of the side walls, the endwalls and the floor being formed from fiber reinforced plastic; a roofmolded as a second fiber reinforced composite structure having a foamcore encapsulated with fiber reinforced plastic; the roof having aninterior surface which defines in part a corresponding interior surfaceof the composite box structure; the roof having an exterior surfacewhich defines in part a corresponding exterior surface of the compositebox structure; the interior surface and the exterior surface of the roofbeing formed from fiber reinforced plastic; and the roof beingadhesively attached to the end walls and the side walls opposite fromthe floor.
 26. A composite box structure for mounting on a railway carunderframe to form an insulated railway boxcar comprising:a pair ofopposite side walls and a pair of opposite end walls extending betweenand joined with the side walls to define in part a hollow interior forthe box structure; a floor extending between and joined with the sidewalls and the end walls; a roof integrally molded with the end walls andthe side walls opposite from the floor; an opening formed in each sidewall intermediate the end walls; and the side walls, the end walls, thefloor, and the roof being formed as an integrally molded fiberreinforced composite unit.